Abstract: Instead of monitoring a thermal deburring operation by reference to whether a certain high temperature is reached and thereby indicting whether a successful ignition in the deburring chamber has taken place at every step of operation of the chamber, a circuit responsive to the rate of change of temperature is used to recognize a successful operation, thus permitting faster operation of the apparatus. Such a circuit is also useful for rapid detection of a short circuit circuit in electrochemical apparatus utilizing heavy electrical currents and variable amounts. In the latter case a digital circuit for measuring the amount of change at equal intervals of time is particularly useful.

Abstract: The high voltage between a rotary disk coating powder dispensing device and an electrically grounded article to be coated is maintained constant when the spacing between a spray disk at high potential and an article to be coated at ground potential is too great to permit a breakdown discharge, whereas at smaller spacings the current flowing as the result of transport of charged coating material is held constant, but when the spacing goes below a minimum value at which the energy stored in the disk device and in the wiring capacitance is sufficient to support a breakdown, the high-voltage supply is switched off, by short-circuiting the high-voltage transformer secondary winding. When the high-voltage supply is thus switched off, an acoustic or optical alarm is actuated to call attention to the necessity of restoring operation.